ELECTROMECHANICAL COUPLING OF 2-2 PIEZO-COMPOSITE MATERIAL

A dynamic model for 2-2 piezo-composite material was developed, in whi ch the acoustic plane waves propagating along the interface were solve d and their dispersion curves were obtained. By taking the resonator t hickness as half a wavelength or its odd fold, the resonant frequencie s of the composite transducers are in agreement with the dispersion cu rves. From the dynamic model the piezoelectric coupling coefficients f or the thickness vibration of the composite could be obtained as a fun ction of the composite thickness as well as the volume fraction of the ceramic phase. The results show that when the thickness vibration mod e is decoupled with the lateral periodical vibration mode, the piezoel ectric coupling reaches its maximum. This condition gives a maximum fr equency bandwidth and a greatest piezoelectric coupling coefficient fo r the composite material.